Hot air heating furnace



D. J. CAMPBELL 2,078,053

HOT AI HEATING FURNACE Filed Feb. 26, 1934 2 Sheets-Sheet 1 April 20 1937.

April 20, 1937. D. .1. CAMPBELL l HOT AIR HEATING FURNACE 2 Sheets-Sheet 2 Filed Feb. 26, 1954 INVENTOR afs/Amd CAMPELL ATTQRNEY i Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE HOT AIR HEATING FURNACE Application February 26, 1934, Serial No. 712,984

7 Claims.

This invention relates to heating furnaces for heating the interior of buildings as dwellings, oilices and the like by causing a circulation of heated air to the room or rooms of such building. This application is a continuation in part of applicants copending application Ser. No. 697,816, filed November 13, 1933.

A primary object of invention is to provide an air heating furnace construction that will heat and cause the circulation of the heated air more efficiently than heretofore.

Another object of invention is to provide an air heating furnace that will consume less fuel than furnaces heretofore constructed.

A further object of invention is to provide a joint between the cas-t sections of the furnace that will not allow escape of gases from the combustion chamber into the circulating air flowing through the furnace.

Yet another object lies in the minimizing of the expansion of adjacent parts by forming the parts of different metals. That is, the part which is heated to the higher temperature has the lesser coefficient of expansion.

The invention provides other novel features that are particularly pointed out in the accompanying drawings, in which:

Fig. 1 is a sectional view through my improved furnace. i

Fig. 2 is a sectional view on line 2-2 of Fig. I, looking downward.

Fig. 3 is a sectional view on line 3 3v of Fig. 1.

Fig. 4 is an enlarged sectional view illustrating applicants novel joint construction.

The furnace is provided with the customary outer shell I, which may be cylindrical, hexagonal, octagonal, or any suitable exterior shape. The lower end of the shell is closed by the floor upon which it sets, which is usually of brick or concrete, and the upper end is closed by a frustoconical cover or bonnet 2 which is provided with suitable conductor flue openings 2a.; within the shell is` located the various parts, principally of cast metal. The furnace body comprises an ash pit 3; lower and upper fire pot sections 4 and 5; upper and lower combustion chambers 6 and 'I. The lower combustion chamber 6, together with the ash pit 3 is provided with extending passages 3a and 6a, respectively, emerging through the shell and each closed by a conventional hinged door. About the lower section 6 of the combustion chamber and resting thereon is the upper section 1 in which the combustion chamber portion is of dome shape as 8 and integral therewith and connecting thereto by conductor ues 9 is the radiator IIJ, which may be described as substantially annular ring shaped, although divided at the front of the furnace. The radiator lil is divided into upper and lower flues II and I2. These flues II and I2 extend from the division I3 to the rear of the furnace and are terminated by the vertical partition walls I4. The iiue I2, divided at I3, communicates at its rear portion with a vertical flue I5 communicating with the escape or stack flue I6.

The plurality of flues 9 extend between the dome 'I and the upper flue Il of the radiator and space the radiator from the dome. The hot products of combustion pass from the dome 'I to the radiator through these flues 9. A rearwardly extending ue I'I controlled by a damper i8 conducts the products of combustion direct to the stack flue, when desired, and by turning the damper I8 the proportionate heated products of combustion can be regulated between that passing through the ilues of the radiator and the ue I1. A suitable rod I9 controls the position of the damper through the crank arm 20 on the damper shaft.

Clean out ues 2| extending through the shell I provide openings through which the interior of the radiator flues II and I2 may be cleaned.

A water receptacle 22 surrounds a portion of the ash pit; the water, being evaporated by the temperature of the ash pit wall, mingles with the air passing upwardly between the furnace shell and the body and through the opening 24, becoming charged with moisture from the evaporation of the water in the receptacle 22. A portion of the air entering the furnace through the cold air duct 23 is deflected by the plate 25 through the opening 26 and passes upward between the shell of the furnace and the body and out through the openings 2a.

The furnace body is provided with a joint as 26 above the lower combustion chamber 6, comprising an upwardly extending flange or collar 2'1 on which the upper section "I of the combustion chamber rests. Horizontal flanges 28 and 29 are provided with the grooves 30 into which is placed a rope packing 3| suitable lugs 32 are provided on the body sections whereby they are securely joined together without preventing individual expansion or contraction of each section independent of any other. The lugs 32 are held in clamped position by means of wrapping wire around the lugs and twisting the ends thereof or by means of a C clamp, whereby when disassembling the sections of the furnace body the C clamp may be driven off, and in the case of the wire it can be cut whereby the upper section can be lifted from the section below without disturbing the packing between the sections and the sections can be re-assembled in the reverse order.

The various members of the furnace body are preferably provided with heat radiating ribs or fins 33, whereby heat transfer from the body' to the air owing through theV furnace is brought to a high degree of eiiciency and in order to increase the heat transfer the upper section 1, which includes the dome 8, flues S and radiator I0 of preferably aluminum alloy Vwhich has ay high heat conduction ratio compared to cast iron or steel from which it is usual to make such parts of furnaces. In some cases, however, these parts are made from a copper or other alloy having a high rate of heat conduction and also a high coefficient of expansion and contraction which unequal expansion and contraction between the sections of the furnace body is taken care of by the joint 26. By this I mean that the joint is so shaped at its inner lower and inner upper side as to cause the actual expansion of these two sections to be more or less the same as will now be fully explained.

As previously explained the upper portion of the furnace, this being the portion which is heated to the least temperature, is formed of a metal which has the greater coecient of expansion. This, of course, tends to cause the upper part of the furnace to expand more than it would otherwise and consequently the expansion of this upper portion of the furnace will more nearly tend to approach the expansion of the portion immediately underneath and therefore there will be less sliding between these two portions. It is apparent that the lower portion will become more highly heated because it is inclose proximity to the flame and this more highly heated portion will expand more because its range. of temperature is greater. I have solved this problem of unequal expansion in a novel manner and consequently the slippage between the two sections is very materially reduced. It is appreciated that there will be some slippage between these two sections, due to their actual differences in expansion, but the actual differences have been minimized to a marked degree by using cast metals of different characterkistics and deflecting the flame at the inner side of the joint. Furthermore, the joint itself, is novelly improved to permit a certain degree of expansion to occur without any permanent distortion of the several parts. In this connection, the packing 3i is not confined within a certain predetermined space, whereby it would act in the nature of a solid, but rather is free to be flexed and moved laterally and thus permit the two sections to slide relatively to one another. With referencev to the deection of the flames I have so shaped my furnace and the joint, see Figs. 1 and 4, as to cause the flames from the coal or the like to pass inwardly immediately below the shoulder between these two sections and thus prevent the impingement of the flames against the upper section. Thus there will be a dividing zone, namely, the juncture between these two sections, and the metal above this zone will be of a definite lesser temperature than the metal below this juncture. Also, see Fig. 4, the open space between the flanges 28 and 29 very materially decreases the heat transfer therebetween. Thus, rst, the sliding between the sections is reduced and, second, what sliding occurs is eiciently and expeditiously taken care of by my novel type of joint.

Operation Although the furnace as illustrated and described is designed to utilize coal as a fuel, it is to be understood that other fuels than coal can be used, such as oil or gas. The fire occurs within the re pot and combustion chamber, these parts being heated by the fire directly and the products thereof which travel upwardly into the dome 8 and radially outward through the flues 9 into the upper flue ii of the radiator IS and downwardly into the flue l?. and from the flue l2 upwardly through the flue l5 at the back of the furnace and to the stack flue I6. The dome S of the section 'l together with the flues 9 and radiator being of aluminum or copper alloy, a rapid heat conduction takes place and the air passing against the radiating ns is heated to a higher degree of temperature per unit of contact area than as if the like parts were of iron or steel, which have a low factor of heat conduction.

It may be here explained that when it is desired to start a fire quickly in the fire pot of the furnace as with coal, for example, the damper i8 is turned to the open position of the flue I1, providing a direct passage from the dome 8 to the stack flue I6 and giving to the fire a strong direct draft Whichl causes the re to build up quickly, but when the re has been established, the damper may be turned to its closed or partly closed position, causing all or only a portion of the hot products of combustion to pass through n the flues 9, Il, l2 and l5 to the stack flue I6, thus causing at will the hot products of combustion to traverse a devious passage and to impart to the radiationv walls the greater portion of their heat. Part of the flow being downward against the force of its gravity tends to slow the rate of flow and thereby causes the flow to contact a greater radiating area both resulting in increasing the heat transfer.

It is to be understood that the furnace is not claimed in its entirety, but is defined in the accompanying claims, and

I claim- 1. In a hot air heating furnace comprising in combination, a nre pot portion and upper and lower combustion chamber portions and a slide joint between the upper and lower combustion chamber portions consisting of an upwardly extending flange on the lower combustion chamber portion upon which the upper combustion chamber portion rests, spaced horizontally extending flanges on each of the combustion chamber portions, each flange being provided with a groove and a flexible packing in the said grooves, said upwardly extending flange being laterally spaced from the upper combustion chamber portion.

2. In a structure of the class described, made up of sections, a joint comprising a flange on one section and a surface on the other section against which the said flange bears, said surface being extended radially with respect to the flange whereby sliding movement may be had therebetween, said sections being cut away so as to form spaced walls at all points except the previously mentioned contacting points, grooves formed in the walls of the sections and a flexible packing located in the grooves and extending between the sections to form a leak-proof joint therebetween. f 3. A hot air heatingl furnace composed of a YAMplurality of sections, comprising among others, a

combustion chamber section, a separate radiator section including a cover for the combustion chamber section in which the radiator section has a greater coefficient of thermal expansion and contraction than the combustion chamber section, and baiile means for shielding the joint between the combustion chamber section and the radiator section.

4. A construction as set forth in claim 2 in which the combustion chamber section has a portion bulged outwardly adjacent the joint for the purpose described.

5. A hot air heating furnace comprising a combustion chamber section, a separate radiator section located immediately thereabove and being subjected to the products of combustion after they have left the combustion chamber section, said radiator section being formed from metal having a greater coefiicient of thermal expansion and contraction than the combustion chamber section, the lower edge of the radiator section being supported by the combustion chamber section, the upper edge of the combustion chamber and said lower edge of the radiator section being thickened and shaped for juncture so as to expose a relatively large percentage of the surface of the upper terminal edge of the combustion chamber to the contact of the products of combustion and a relatively small percentage of the surface of the lower terminal edge of the radiator section thereto whereby the averages of the temperatures in the respective sections is very materially different thus minimizing the actual sliding between the sections.

6. In a structure of the class described, made up of substantially circular sections, a joint comprising a continuous upwardly extending flange on the lower section and a surface on the upper section against which the said ange bears, said surface being extended radially outward with respect to the flange whereby limited sliding movement may be had therebetween, said surface then extending downwardly to form a shoulder spaced outwardly from said flange a predetermined distance, said sections being cut away so as to form spaced Walls at all points except the previously mentioned contacting surfaces, grooves formed in the walls of the sections and a flexible packing located in the grooves and extending between the sections to form a leak-proof joint therebetween.

7. In a structure of the class described, made up of substantially circular detachable vertically disposed sections, a joint between said sections comprising an annular upwardly extendng ange on the lower of two sections and having a bearing surface and a radially disposed surface on the upper of said sections against which the said flange bears, whereby a relative sliding movement of the said sections may be had therebetween, a downwardly extending annular surface on the said upper section in radially spaced relation to said upwardly extending flange limiting the said relative sliding movement, a radially disposed surface in spaced relation on each of said sections, opposed grooves in the last named surfaces and a yieldable packing in said grooves and between said last named surfaces to form a leak-proof joint therebetween.

DONALD J. CAMPBELL. 

